1) Field of the Invention
The present invention relates to a process for producing an amino composition by addition reaction between a polyamine and an unsaturated hydrocarbon compound. The amino composition obtainable by the process according to the present invention has reactivity with epoxy resins, isocyanates and the like, and is useful as curing agents for epoxy resins or chain extenders for polyurethane resins.
2) Related Art
An amino composition obtained by the addition reaction of a polyamine with an unsaturated hydrocarbon compound has low viscosity and is useful for the reason that, for example, an epoxy resin composition which contains curing agents for epoxy resins comprising said amino composition provides an epoxy resin cured product excellent in various properties.
The process for producing the above-mentioned amino composition by addition reaction between a polyamine and an unsaturated hydrocarbon compound in the presence of a strongly basic alkali metal catalyst has been publicly known (Japanese Patent Kokai No. 2002-161076).
The amino composition obtainable by the process directed in the above Japanese Patent Publication, however, generally contains unreacted polyamine as a residual. When the amino composition contains such residual unsaturated polyamine, an epoxy resin composition using the amino composition as an epoxy resin curing agent may have such defects that the appearance of a coating film tends to be inferior by the phenomena of whitening or tackiness because carbamate or carbonate of polyamine may easily be produced by absorbing carbon dioxide or water vapor in the atmosphere. Especially, the carbamate produced in the case of using metaxylylenediamine as a polyamine is readily crystallized and the phenomenon of whitening tends to occur easily.
It has been known that reducing the content of unreacted polyamine in the amino composition is effective for recovering such defects of the amino composition. As a general method for reducing the content of unreacted polyamine, it is possible to increase the reaction ratio of the unsaturated hydrocarbon compound to the polyamine.
However, in the case of using the amino composition thus obtained as an epoxy resin curing agent, for example, such amino composition has defects not only that the amount of the amino composition as a curing agent to be blended in an epoxy resin may become large, but also that the reaction point of the amino composition to be reacted with epoxy groups of an epoxy resin may be reduced which will cause that the network structure in an epoxy resin cured product may not be formed sufficiently and the satisfactory properties can not be obtained.
On the other hand, unreacted polyamine contained in the amino composition can be removed by using methods such as vacuum distillation. However, polyamines useful for curing agents generally have high boiling point. Therefore, in order to remove unreacted polyamine to the degree wherein the appearance of coating films can be improved sufficiently using a usual method of distillation under reduced pressure, distillation under a high temperature or under highly reduced pressure may be required.
In general, amines may work undesirable changes such as coloration when various operations are conducted with them under a high temperature. In addition, apparatuses requiring high vacuum condition such as a thin-film evaporator are usually expensive. From the above view points, it has been expected to develop another convenient method for removing unreacted polyamine.
Moreover, shortly after being produced, the amino composition usually expresses a transparent liquid having low viscosity. However, regardless of the presence of unreacted polyamine, the amino composition may change over time (for example, increase of viscosity and/or generation of white solid may occur), which may cause not only the remarkable deterioration of commercial value of the amino composition but also the deterioration of physical properties of an epoxy resin cured product derived from an epoxy resin composition containing said amino composition. Therefore, development of a method for producing an amino composition excellent in storage stability has been expected.